As vehicle helmets worn by a motorcycle rider or the like, a full-face-type helmet and a jet-type helmet are conventionally known. In the full-face-type helmet, a chin cover for covering the wearer's chin is integrally formed with the cap portion. In the jet-type helmet, no chin cover is formed on the cap portion so as to expose the face of the wearer substantially entirely. Another full-face-type helmet (to be referred to as a “full-face-type helmet serving also as a jet-type helmet” hereinafter) is also conventionally known, as is disclosed in U.S. Pat. No. 6,226,803 B1. In this full-face-type helmet, the cap portion comprises a main cap portion having substantially the same shape as that of the cap portion of a jet-type helmet, and a subsidiary cap portion attached to the main cap portion to be vertically pivotal so as to selectively cover the wear's chin, so that the helmet can have the functions of both a full-face-type helmet and a jet-type helmet.
In the conventional full-face-type helmet disclosed in U.S. Pat. No. 6,226,803 B1 and serving also as the jet-type helmet, when the subsidiary cap portion is at the lower position (i.e., in the lower state) or backward position (i.e., in the backward state), the subsidiary cap portion serves as a chin cover means. When the subsidiary cap portion is at the upper position (i.e., in the upper state) or forward position (i.e., in the forward state), a large window formed in the main cap portion is opened entirely, and the cap portion accordingly does not have a chin cover means, in the same manner as in the jet-type helmet. When the wearer wearing the full-face-type helmet serving also as the jet-type helmet, as disclosed in U.S. Pat. No. 6,226,803 B1, is driving a motor cycle at high speed, the helmet is worn with its subsidiary cap portion being lowered to the lower position, in order to prevent a large wind pressure from acting on the wearer's chin and its vicinity. The helmet of U.S. Pat. No. 6,226,803 B1 is also provided with a subsidiary cap portion locking mechanism for locking the subsidiary cap portion at the lower position with respect to the main cap portion, so that a large impact or wind pressure does not undesirably let the subsidiary cap portion move upward during high-speed driving. Furthermore, the subsidiary cap portion locking mechanism in the helmet of U.S. Pat. No. 6,226,803 B1 comprises a release button serving as an unlocking means or unlocking member so as to unlock the subsidiary cap portion locked at the lower position. When the wearer presses the release button for unlocking, the subsidiary cap portion at the lower position is unlocked.
In the full-face-type helmet serving also as the jet-type helmet as described above disclosed in U.S. Pat. No. 6,226,803 B1, while the wearer wears the helmet with the subsidiary cap portion being lowered to the lower position, when a comparatively large impact acts on the helmet in a direction to move the subsidiary cap portion upward, even if the wearer does not press the release button to unlock, the subsidiary cap portion may accidentally move upward. The reason for this will be described with reference to FIG. 15.
FIG. 15 shows the mutual positional relationship, seen from the side direction (that is, the side), among an attaching screw 7, lock lever 83 and lock pin 92 of the cap portion of the helmet of U.S. Pat. No. 6,226,803 B1 with the lower end opening of the cap portion of the helmet being substantially horizontal. Regarding the reference numerals of the respective portions in FIG. 15, portions that are common with those in FIG. 14 of an embodiment of the present invention (this FIG. 14 is a view similar to FIG. 15) are denoted by the same reference numerals. In FIG. 15, the attaching screw (axial support means) 7 attaches a subsidiary cap portion 6 to a main cap portion 5 to be reciprocally pivotal. A rivet 84 pivotally attaches the lock lever 83 to an attaching base (not shown). The lock lever 83 has a locking recess 94. In the state of FIG. 15 (that is, when the subsidiary cap portion 6 is in the lower state), the lock pin 92 engages with the locking recess 94. The lock lever 83 is also provided with a wire attached portion 86 and stopped portion 85. A spherical body 119, having a free end to which a tractive wire portion 75c fixes, attaches to the wire attached portion 86. The stopped portion 85 is inserted in an incision in the attaching base.
In FIG. 15 which shows the helmet of U.S. Pat. No. 6,226,803 B1, reference symbol L1 denotes the first straight line extending from the center of the attaching screw 7 to the center of the lock pin 92. The intermediate portion of the first straight line L1 is omitted. Reference symbol L2 denotes the second straight line obtained by extending the first straight line L1 from the center of the lock pin 92 in a direction opposite to the center of the attaching screw 7 so as to be identical with the first straight line L1. Reference symbol L3 denotes the third straight line extending from the center of the lock pin 92 in a direction along which the lock pin 92 starts to relatively disengage from the locking recess 94 upon forward pivot motion (that is, clockwise pivot motion in FIG. 15) of the lock lever 83 about the center of the rivet (axial support means) 84 as the pivot fulcrum. The third straight line L3 is substantially perpendicular to a fourth straight line L4 which connects the center of the rivet 84 to the center of the lock pin 92 and faces in a direction substantially opposite to the second straight line L2. Hence, an angle θ1 that the third straight line L3 forms with the second straight line L2 is substantially equal to or near 180° (more specifically, an upward angle of about 175°).
In FIG. 15 which shows the helmet of U.S. Pat. No. 6,226,803 B1, the angle θ1 that the second straight line L2 forms with the third straight line L3 is substantially equal to or near 180°. Hence, the pivot direction along which the subsidiary cap portion 6 starts to move upward and the pivot direction along which the lock lever 83 starts to pivot forward about the rivet 84 as the fulcrum so as to relatively disengage the lock pin 92 from the locking recess 94 face substantially the same side (in other words, clockwise in FIG. 15). Therefore, assume that a comparatively large impact that is to pivot the subsidiary cap portion 6 forward from the backward position shown in FIG. 15 acts on the helmet. If the lock lever 83, rivet 84, lock pin 92, or the like deforms elastically or in other manners, the lock pin 92 accidentally disengages relatively from the locking recess 94 of the lock lever 83, and the subsidiary cap portion 6 may pivot forward about the attaching screw 7 as the fulcrum undesirably to accidentally move upward, partly because an elastic biasing means such as a spring biases the subsidiary cap portion 6 in the forward pivot direction.